Use external SMTP server on Mantis bugtracker

[mantis]# cat config_inc.php
# --- email variables -------------
$g_smtp_host = 'smtp.domain.com';
$g_smtp_username = 'user_id';
$g_smtp_password = 'user_password';
$g_use_phpMailer = 'ON';
# We do not use sendmail.
$g_phpMailer_method = '2';
?>
[mantis]#